1. Field of the Invention
The present invention relates to a radio communication system for connecting a communication station to a cellular phone in response to a connection request from the communication station and, more particularly, to a communication technique of a radio communication system including: a server performing a connection request process to a cellular phone in response to a connection request from a communication station; and a communication device connected to a server to communicate with a cellular phone.
2. Description of the Background Art
In a system utilizing radio communication, differently in situation from that utilizing wire communication, communication with a radio base station cannot be always established, depending on whether a cellular phone exists in a range where radio waves from a radio base station reaches, whether a cellular phone is in a wait state or the like. Therefore, even when a connection request is transmitted from the communication station, the cellular phone cannot receive the request and cannot establish the connection with the communication station.
Japanese Patent Laying-Open No. 5-102924 discloses a cellular phone which switches over two types of communication circuits and responds to a call transmitted from a master station. The cellular phone disclosed therein includes: a circuit forming a radio channel (main line) with a radio base station; a call reception circuit receiving a call originating from a master station and transmitted from a radio transmission station in a wait state; and a circuit turning off a cellular phone main body when no communication channel is formed.
According to the cellular phone disclosed in this publication, while the cellular phone is in a wait state, only the radio call reception circuit is turned on, the cellular phone main body is turned off, and the radio channel (main line) is turned off. The cellular phone main body is turned on only when the cellular phone responds to or communicates with the radio base station. With this structure, even when no radio channel is formed, the call reception circuit can detect a call transmitted from the radio transmission station. In addition, in the wait state, the cellular phone main body, i.e., the battery thereof is turned off, thereby making it possible to suppress power consumption from being wasted.
However, the radio call reception circuit of the cellular phone disclosed in this publication deals only with reception. Therefore, when the main circuit is turned off and the system is unusable, the detailed state of the cellular phone (in which the cellular phone is out of the range of the radio base station, the cellular phone is turned off, there is no empty communication channel of the radio base station for the cellular phone, the cellular phone is holding a communication, the cellular phone is out of order or the like) is not notified to the master station. As a result, an originator is disadvantageously incapable of knowing the reason why the communication cannot be established.
Furthermore, even when the main line is usable, the following disadvantages arises due to the fact that the radio call reception circuit deals only with reception. In establishing communication between the cellular phone and the radio base station, authentication information and connection information common to the cellular phone and the radio base station are required. However, since these pieces of information cannot be instantly shared between the cellular phone and the radio base station, it is necessary to register the information in advance.